Method of producing dye images



June 6, 1944. G, EHRENFRIED 2,350,736

METHOD OF PRODUCING DYE IMAGES y Filed July l0, 1942 'f' v FIGJ.

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HMT/0N 53 Maw/va s/L vf/e 73 I3 l5 f5 12 2z f2 52 33 REHALocf/v/zAr/ov GEORGE EHRENFRIED 'l INVENTOR BY 4am mx,4

. 35. M Lf/mn@ A TTORNEYS Patented June 6, 1944 Mn'rnon oF raonUcING DYE IMAGES ,l George Ehrenfried, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application July 10, 1942, Serial No. 450,386

This invention relates to a method for pro- .ducing colored photographic images and particularly lto a method of forming colored images in a dye-bleaching process of color photography.

Christensen, U. S. Patent 1,517,049, November 25, 1924, describes a.process for producing a dye image in which a dyed gelatin layer containing a silver image is treated with a solution of a strong reducing agent such as sodium hydrosulte or stannous chloride. The reducing bleach bath destroys the dye in the layers selectively in the region of the silver image, giving a. positive dye image from a negative silver image. The destruction of a dye to form a photographic image in this process appears to depend upon the catalytic vaction of the silver image which results in the destruction of the dye in that portion of the film when treated with a suitable reducing bleach bath.

I have found that in some cases image-form- -ing dyes used in this process may be more readily bleached if a freshly developed silver image is used ,rather than a silver image which has been washed or which has been treated with a fixing bath subsequent to reduction.

It is, therefore, an object of my invention to provide a novel method of forming a colored photographic image in a photographic layer. A further' object is to provide anovel method for destroying a dye uniformly dispersed in a photographic layer under influence of a redeveloped sll/er image. Other objects will appear hereinaf er. I

These objects are preferably accomplished, according to my invention, by exposing and developing the emulsionlayer containing the uniform dispersion of image-forming dye, fixing, rehalogenizing the silver image thus formed, redeveloping the rehal'ogenized silver image, then treatving the layer with a solution of a suitable reducing bleaching agent to bleach the dye from the layer in the region of the silver image.

Other objects are accomplished by repeating `as many times as required the steps of rehalogenizing,redeveloping and bleaching in order that any dye remaining unbleached in the region of the silver image, may be bleached from the layer.

The'photographic element treated according to my invention may comprise a single emulsion layer or a plurality of emulsion layers coated on one or both sides `of a suitable support. This 13 claims. (c1. sis-ss) a uniformly dispersed dye prior to exposure ora dye intermediate in which a colored compound may be formed after exposure. I prefer to, use

-certainbleachable dyes of the general class of poly-azo dyes as disclosed in Christensen U. S.

' Patent 1,517,049, though not necessarily the same dyes, and bleachable azo dy'es such as disclosed in my prior U. S. Patent 2,322,001, granted June 15, 1943. Certain bleachable vat dyes, as for instance those disclosed in Seymour U. S. Patent 2,184,022, granted December 19, 1939, are likeeach of which is roughly complementary in colsupport may be a cellulosic material such as pigmented cellulosic material,.synthetic resin or paper. The emulsion layer vor layers may contain wise suitable.

If a three-layer photographic element is used for the production of natural color images, lthe three emulsion layers preferably contain dyes,

or to the effective sensitivity ofthe emulsion layer. The red, green and blue sensitive emulsion their sensitivity with azo dyes as shown in my prior application above-cited, or with vat dyes such as those shown in the above Seymour patent. v

'I'he layers need not be colored complementary to their'sensitivity, however, but may be colored alternatively with a dye that transmits the colors for which the layers are mainly sensitive.

' My invention is'illustrated by Figs..1 and 2 of the accompanying drawing. In the drawing. Fig. 1 shows in enlarged cross-sectional view the appearance of a color film in iive stages of processing in accordance with the preferred manner of my invention. Fig. 2 shows in enlarged cross-sectional view the appearance of a color film which has been incompletely bleached in the processing `steps illustrated in Fig. l. which nlm is subjected lto the processing steps shown in the last three stages of Fig. 1 in order 'to complete the bleaching of the dyes in the emulsion layers.

, A film of the type shown in the rst stage of v Fig. 1 of the 4drawing or a single layer lm,-hav ing emulsion layers or layer colored in relation to the sensitivity as described in my prior application, i.' e. colored complementary to the sensitivity, is exposed in a camera or` under a suitable color positive or negative. For example, it may be exposed to a natural color transparency by a single exposure to'tungsten light through suitable correctinglters or by three lsimultaneous or successive exposures to light transmitted by red, green and blueiilters in 'a suitable ratio of times and intensities. The lm is then developed in an ordinary black-and-white developer, washed and fixed. The silver image or bath as for instance alkali stannite solution, neu- 5 tral, or slightly acid or'alkaline sodium hydrosulflte, etc., with or without the addition of chemicals capable of accelerating bleaching. It is," according to myinvention, the steps` of redeveloping the rehalogenized silver image and lil using it for the bleaching of dye in an emulsion layer, which enhance` the bleaching activity of the silver for dyes,particularly for dyes which are not readily bleached by the first developed silver image. Typical of such difcultly bleached dyes are Pontamine Fast Green 5BL and tetrazotzed 4,4' diamino 3,3',6,6' tetramethyl` triphenylmethane coupled with N-heptoyl H acid. I have also found that in certain cases where the dyes are not completely bleached in the usual Water to time of bleaching, in presence of the freshly developed silver image, it is advantageous to repeat f the steps of rehalogenization, redevelopment land bleaching'. These added Iprocessing steps appear to be necessitated, by certain of the dyes used,

i. e. the difIlculty-with which certain dyes are bleached, and also by the characterof the developed silver image. 'I'hat is. a freshly developed silver image may have a much greater influence for bleaching dyes than an originally developedsilver image which has been fixed and washed, so that the effective bleaching activity of the image may be enhanced by again producing it in the freshly developed state and using it to bleach more dye.

This part of my process wherein the steps of rehalogenization, redevelopment and bleaching are repeated, constitutes a cycle of steps which may be repeated as often as desired or as required by the particular color process in use.

In the process described in my prior application above-cited, wherein dyes are bleached under inuence of a rehalogenized silver image, I also find that the steps of rehalogenizlng and bleaching are advantageously repeated to obtain more effective or efficient bleaching of dyes in a photographic layer. Y

My invention will now be described by example and with particular reference to the figures of the accompanying drawing.

Fig. 1 shows a color ill'm having emulsion layyers colored in the manner described in my prior application, that is,.the film has a support I0 of a cellulose ester or other suitable material carrying emulsion layers Il, I2, and I3 sensitized to red. 55

green and blue light, and colored cyan, magenta and yellow, respectively.- Layer I5 is a separating colloid layer containing a yellow filter material, as for example, colloidal silver, and layer Il contains colorless colloidal material such as gelatin. 80

'I'he film of Fig. 1 is exposed to a natural color transparency by a single exposure to tungsten light through suitable correcting filters. The nlm is then developed for about eight minutes at 68 F. in a tank of the following developer:

Monomethyl-p-aminophenol I'he print is now placed for two minutes in a stop bath consisting of: acetic acid, 28 per cent, 500 cc.; water 4 liters.

The nim is then thoroughly fixed in acid hypo solution of the following composition:

Water (about 125 F.) cc-- .600 Hypo grams-.. 240 Sodium aulfitn dn 15 Acetic acid (28%) ..cc 48 Boric acid crystals grams..- '1.5 Potassium hun dn 15 Water to liter-- 1 The nlm now appears as shown in the second `stage of Fig. 1 wherein the emulsion layers Il,

I2, and I3 contain negativesilver in areas 2|, 22, and 23, respectively in addition to dye.

The silver images produced by the development are bleached to silver chloride by treatment for about ten minutes in the following solution:

Cuprlc chloride grams-- 100 Hydrochloric acid, concentrated cc-- 25 liter-- l The film now appears as shown in the third stage of Fig. l wherein the emulsion layers II, I2, and I3 contain the rehalogenized silver images 3l, 32, and 33 respectively, and the emulsion layers are still uniformly colored throughout. 'jj

The film after exposure is then redevelopefd in the above black-and-white developer and appears as shown in the fourth stage of Fig'. 1 of the accompanying drawing, wherein the emulsion layers II, I2, and I3 contain freshly developed silver images in areas 4I, 42, and 43 respectively.

Without washing, the film is next placed in an alkaline stannous chloride solution which bleaches dyes selectively in the presence of the freshly developed silver images. The following sodium stannite solution is suitable for this purpose:

Stannous chloride grams-- 8 v The film is now washed in water. The silver images are then bleached in the same copper chloride bath Apreviously used, to convert them to silver chloride, and thereafter, the silver chloride is removed from the emulsion layers by fixing in acid hypo bath of the same composition as that previously used.

The film appears as shown in the fifth stageof Fig. 1 wherein the layersv Il, I2, and I3 have clear areas in the portions 5I, 52 and 53 respectively. Layer I5 is clear, the filter material having been removed during the process of treatment with the cupric chloride and nxing solutions.

As mentioned above, I sometimes nd that even by application of the novel method above described, the dyes may not be completely removed from the emulsion layers in areas from which it is intended that they should be removed to give a picture in natural colors. I have shown the appearance of a film of the type shown in therst stage of Fig. 1, which vhas been exposed, developed, fixed, rehalogenized,

redeveloped, and bleached, and in which emulsion layer I3 is shown as having a completely bleached area 63, whereas areas 6I and 62 of layers II and I 2 represent cyan and magenta dyes, respectively,

which have not been removed during bleaching.

According to another feature of my invention I take this lmshown in Fig. 2 of the accompanying drawing and repeat the steps of rehalogenizing, redeveloping and bleaching to obtain complete removal of dye in areas 6I and 32.

'Il Thereafter, the silver images remaining in the In Fig. y2,

layers are converted to silver chloride by use of the same cupric chloride solution mentioned above and the resulting silver chloride images are removed with a hypo solution of the com position given above. The nlm then appears as shown in the fifth stage of Fig. ll the areas corresponding to I, 52, and l! being clear.

c In place of the copper chloride bleach bath used to convert the -silver images to silver chloride, baths of the following composition may be used:

A. Quinone, hydrochloric acid and ethyl alcohol. B. Ferrie chloride and hydrochloric acid.Y

C. Ammonium persulfate and hydrochloric acid.

In some cases it is desirable to add an organic solvent to the sodium Stannite bleach bath to reduce highlight stain. One volume 'of tertiary butyl alcohol to about ten volumes of the bleach bath appears to be a satisfactory solvent for this purpose.

Other dyes which, for example, may be. bleached in the manner of my invention are: Diphenyl Fast Green BL. Diamine Golden yellow No. 529 Schultz 7th ed. 1931, Brilliant Carmine Ls No. 327 Schultz 7th ed'. 1931, tetramtized 4,4'1

diaminotriphenylmethane coupled with N-lauroyl H-acid, Diphenyl Brilliant Pink B.

It is to be understood that the disclosure herein is byway of example and that I consider as included in my invention all modifications and equivalents falling within the scope of the appended claims. s

What I claim is:

1. 'I'he method of forming a colored image in a photographic layer containing uniformly disvpersed therein a dye bleachable with a reducing bleach bath under influence of a silver image and a silver image, which comprises rehalogenizing said silver image, converting said rehalogenized image to a silver image, and without intervening treatment, bleaching the dye in the region of the freshly reveloped silver-image with a reducing bleach bath.

2. The method of forming acolored image in a photographic layer containing uniformly dispersed therein a bleachable dye selected from the group consisting of bleachable azo and vat dyes and a silver image, which comprises rehalogenizlng said silver image. converting said rehalogenized image to asilver image, and immediately and without intervening treatment. bleaching the dye in the region of the freshly developed silver image with a reducing bleach bath.

3. The method of forming a colored image in a photographic layer containing a bleachable dye a photographic layer containing a bleachable am dye uniformly dispersed therein and a silver image, which comprises rehalogenizing said silver image. converting said rehalogenized image to a v6. 'I'he method of forming a colored image in a photographic layer containing a bleachable f vat dye uniformlyl dispersed therein and a silver selected from the group consisting of bleachable y azo and vat dyes uniformly dispersed therein and a silver image, which comprises rehalogenizing said silver image. converting said rehalogenized image to a silver image, and immediately and without 'intervening treatment, bleaching the dyein the region of the freshly developed silver image with an alkaline reducing bleach bath.

4. The method of forming a colored image in a photographic layer containing a bleachable am dye uniformly dispersed therein and a silver image, which comprises rehalogenizing said silver image, converting said rehalogenized image to a silver image, and immediately and without intervening treatment, bleaching the dye in the region of the freshly developed silver image Vwith an alkaline reducing bleach bath.

5. The method of forming a colored image in image. which comprises rehalogenizing said silver image, converting said rehalogenized image to a silver image, and immediately and without intervening treatment, bleaching the dye in the region of the freshly developed silver image with an alkaline reducing bleach bath.

7. The method of forming a colored image in a photographic layer containing a bleachable vat ldye uniformly dispersed therein anda silver image, which comprises rehalogenizing said silver image, converting said rehalogenized image to a silver image, and immediately' and without intervening treatment, bleaching the dye in the region of the freshly -developed -silver image withl an alkali stannite bleach bath.

8. The method of forming a colored image in a photographic layer containing uniformly dispersed therein a dye bleachable with reducing bleach bath under influence of a silver image, and a silver image, which comprises carrying out a plurality of cycles of rehalogenizing said silver image, converting said rehalogenized image t0 a silver image, and immediately and without intervening treatment, bleaching the dye in the region of the freshly developed silver image with a reducing bleach bath.

'9. The method of forming a colored image in a photographic layer containing1 uniformly dispersed therein a bleachable dye selected from the group consisting of bleachable azo and vat dyes and a silver image, which comprises carrying out a' plurality of cycles of rehalogenizing said silver image, converting said rehalogenized silver image to a silver image, and immediately and without intervening treatment, bleaching the dye in the region of the freshly developed silver image Awith a reducing bleach bath.

10. The method of forming a colored image in a photographic layer containing a bleachable dye selected from the group consisting of bleachable azo and vat' dyes uniformly dispersed therein and a silver image, which comprises carrying out a plurality of cycles of rehalogenizing said silver image, converting said rehalogenized image to a silver image, and immediately and without intervening treatment, bleaching the dye in the region of the freshly developed silver image with an alkaline reducing bleach bath,

ll. The method of forming a colored image in a photographic layer containing a bleachable azov dye uniformly dispersed therein and a silver image, which comprises carrying out a plurality` of cycles of rehalogenizing said silver image, converting said rehalogenized image to a silver image, and immediately and without intervening treatment, bleaching the dye in the region of the freshly developed silver image with an alkaline reducing bleach bath.

12. The method of forming a colored image in la photographic layer containing a bleachable azo dye uniformly dispersed therein and a silver s image, which comprises carrying out a plurality of cycles of rehalogenizing said silver image, converting said rehalogenized image to a silver image,

4 y. y Y 1 :,stonse and immediately and without intervening treatl l image. which comprises rehalogenizin said silver image, converting said rehalogenized image to a silver image, immediately and without intervenlo ing treatment, bleaching the dye in the redon ofv tnei'reshiy developed silver image with, an alkali stannite ,bleach bath, xehalogenising said last-mentioned silver, image, converting said lastmentioned rehalosenized image to s silver image.

and immediately and withoutintervening treatment. bleaching any dye remaining xn the reden of said last-mentioned silver image with an 'alkali stmnitel bleach bath.-

' GEORGE 

